A disproportionation reaction and/or a trans-alkylation reaction of aromatic hydrocarbons in production of benzene and xylene by disproportionation of toluene, production of xylene by trans-alkylation of toluene and trimethylbenzene or the like is an industrially important reaction, and a large number of catalyst systems have been so far proposed. In recent years, crystalline aluminosilicate zeolites such as faujasite and mordenite have been found to be effective catalysts. Especially, mordenite has a high disproportionation activity or trans-alkylation activity of aromatic hydrocarbons.
However, U.S. Pat. No. 3,729,521 discloses that mordenite alone is not satisfactory with respect to an activity and a catalytic life and a combination of mordenite with metals belonging to the VIB Group, such as chromium, molybdenum and tungsten or metals belonging to the VIII Group, such as iron, cobalt, nickel and platinum is used to improve the activity and the catalytic life. Further, Japanese Patent Publication No. 45,849/1987 discloses a catalyst composed substantially of a mordenite component and a rhenium component. Nevertheless, this catalyst does not exhibit a satisfactory catalytic activity in a disproportionation reaction and/or a trans-alkylation reaction by which to produce xylene from feedstock containing aromatic hydrocarbons.
Further, there is a process for industrially producing xylene from C.sub.9 aromatic hydrocarbons as feedstock with the aid of an amorphous silica-alumina catalyst (PETROTECH, 2(12) 1160, 1970). This process is problematic in that the catalyst has to be continuously regenerated using a moving bed because the yield and the activity are notably decreased over the course of time.
A trans-alkylation reaction of feedstock containing C.sub.9 alkyl aromatic hydrocarbons with the aid of a zeolite catalyst has been reported [I. Wang, T. -C. et al., Ind. Chem. Res. 29 (1990) 2005]. However, the yield of xylene formed is not necessarily high. There has been so far no efficient process for producing xylene from C.sub.9 aromatic hydrocarbons.